It is known to fabricate skateboard wheels from different types of material. For example, semi-hard rubber will provide a comfortable, shock-absorbing wheel structure and a relatively high coefficient of friction with the ground to provide good traction. On the other hand, the rubber itself tends to wear out relatively quickly and the high coefficient of friction results in a relatively low speed wheel.
An alternative known in the art is to fabricate the skateboard wheel from solid plastic such as urethane. These wheels have a relatively low coefficient of friction with the ground and accordingly provide for high speed and as a consequence have gained considerable popularity in recent years. On the other hand, the relatively low coefficient of friction results in poor traction which can be serious in lateral directions. The poor traction characteristics can be overcome to some extent by making the plastic such as urethane softer but by so increasing the traction, the speed of the wheels is decreased. Essentially, while the plastic or urethane type wheels are still in wide use, they all represent a compromise between speed and traction.
Even more recently, it has been proposed in the prior art to combine both the urethane and rubber in a single composite skateboard wheel thereby gaining certain advantages inherent in each material. In such known composite type wheels, a first annular portion of the wheel is made of urethane and a second annular portion of rubber bonded with the urethane. A major problem associated with such type of composite skateboard wheels has been in bonding the materials together. More particularly, there is a tendency for the rubber to separate from the urethane. A result of such separation is a greatly reduced speed, uneven wear and a rougher ride due to the tendency of the rubber material to deform and stretch.
Another problem associated not only with composite type skateboard wheels as described above, but with skateboard wheels in general is the relatively sharp peripheral edges of the wheel resulting from the manufacturing operation. Thus, the ground contacting portion of the wheel extends the entire distance of the overall width of the wheel, there being defined essentially a right angle at the inner and outer peripheral edges of the ground contacting portion with the opposite faces of the wheel. As a consequence, transition of a skateboard upon which the wheel is mounted over a ground ridge running at a very small acute angle; that is, almost parallel to the direction of motion of the skateboard, or over specially designed ridges in skating surfaces, is difficult and dangerous. Moreover, the sharp or extremely small radiused peripheral edges, if any, of such wheels results in chipping and uneven wearing of the urethane and/or rubber materials. Such chipping in the case of rubber results in rapid deterioration.